This description relates to classifying microbeads in near-field (e.g., contact) imaging.
Fluorescent microbeads, for example, are sometimes used in assays as labels for target elements (for example, antigens) that become bound to the microbeads. Microbeads having different known fluorescence spectra when stimulated by a source of light of known spectral properties can be bound to respective specificities of (capture) antibodies. The presence of different kinds of antigens in a sample can then be determined by incorporating in the sample the various different microbeads and additional (detection) antibodies with specificities for the same set of antigens, so that the antigens bind both to the capture antibodies and the detection antibodies. If all the detection antibodies are conjugated to an identical fluorophore with emission different from the beads, by illuminating the sample using light of known source spectra and detecting the resulting localized fluorescence spectra emitted by the microbeads and their bound detection antibodies, it is possible to determine the presence and concentration within the sample of the various different individual antigens of particular classes. In this sense, by classifying the microbeads according to their fluorescence spectra, the antigens can in turn be classified and quantified.
(See Luminex Multiplex Assays, https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-assays-analysis/luminex-multiplex-assays.html?gclid=CjOKCQiAjO_QBRC4ARIsAD2FsXOUygv-JRllcjeahqmk8Yd9gxKTx8Rq5PhI_b9PTwYb2PbBGuvjNfwaAvw6EALw_wcB&s_kwcid=AL!3652!3!211105705124!e!!g!!luminex%20assay&ef_id=Wfz7gAAAAIMHHhyY:20171127205444:s)